1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head which performs a recording action by applying a recording magnetic field perpendicularly to a recording medium.
2. Related Background Art
As is well-known, a perpendicular magnetic recording head includes a main magnetic pole layer and a return yoke layer which are laminated with a predetermined distance therebetween on a surface opposing a recording medium, a nonmagnetic insulating layer interposed between the main magnetic pole layer and return yoke layer, and a recording coil which is arranged within the nonmagnetic insulating layer and applies a recording magnetic field to the main magnetic pole layer and return yoke layer. The main magnetic pole layer and return yoke layer are magnetically coupled to each other on the deeper side in the height direction of the medium-opposing surface. When a recording magnetic field is induced between the main magnetic pole layer and return yoke layer upon energization of the recording coil, a leakage recording magnetic field occurs between the main magnetic pole layer and return yoke layer on the medium-opposing surface. This recording magnetic field perpendicularly enters a hard magnetic film of the recording medium from the front end face of the main magnetic pole layer opposing the recording medium and returns to the return yoke layer through a soft magnetic film of the recording medium. This subjects the recording medium to magnetic recording at a part opposing the front end face of the main magnetic pole layer. Typically, a nonmagnetic layer made of a nonmagnetic material such as Al2O3 or SiO2, for example, is formed about the return yoke layer in order to secure a patterning precision in each of layers laminated on the upper side of the return yoke layer and is flattened such that the upper face of the nonmagnetic layer is flush with the upper face of the return yoke layer.
It has conventionally been common for such perpendicular magnetic recording heads to have a return yoke layer with a rectangular two-dimensional form. However, it has become clear that, when the return yoke layer has a rectangular two-dimensional form, external magnetic fields and recording magnetic fields returning from the recording medium are likely to concentrate on corners (right-angled parts) formed by the front end face exposed at the medium-opposing surface and both end faces in the track width direction, and that the concentration of magnetic fields turns the magnetization of the corner parts in the return yoke layer to a direction perpendicular to the medium-opposing surface, whereby leakage magnetic fluxes from the corner parts cause unintentional recording and erasing on the recording medium.
For preventing the return yoke layer from causing unintentional recording and erasing, it has been proposed, for example, to form both sides in the track direction of the return yoke layer with a tilted surface or curved surface gradually increasing the size in the track width direction of the return yoke layer in the height direction from the front end face exposed at the medium-opposing surface (e.g., Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-039148), Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-127407), and Patent Document 3 (Japanese Patent Application Laid-Open No. 2006-114160)). When the external magnetic fields and the recording magnetic fields returning from the recording medium are absorbed by a wide area of the tilted surface or curved surface, the concentration of magnetic fields is alleviated, whereby the unintentional recording and erasing by the return yoke layer can be suppressed. Patent Document 4 (Japanese Patent Application Laid-Open No. 2004-326990) and Patent document 5 (Japanese Patent Application Laid-Open No. 2006-209818) also disclose relative techniques. Specifically, they propose the magnetic recording head having auxiliary magnetic pole with multilayer structure which a magnetic layer and a nonmagnetic layer are successively laminated.